Browsing by Author "Karthikeyan, S.S."

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    Low-cost fabrication and comparative evaluation of machine learning algorithms for flexible PDMS-based hexagonal patch antenna
    (Nature Research, 2025-08-18) Sarvesan, Srivatsan; Reddy, Mettu Goutham; Karthikeyan, S.S.; Sekhar, Praveen K.
    This article focuses on the design and development of a flexible hexagonal microstrip patch antenna fabricated on a Polydimethylsiloxane (PDMS) substrate for potential use in 5G and wearable applications. The antenna geometry was selected to operate in a higher-order resonant mode to enhance performance under mechanical bending. To accelerate the design process and determine the most effective model for predicting optimal geometrical parameters that yield improved impedance matching at the target frequency, four supervised machine learning algorithms including Random Forest, XGBoost, CatBoost and LightGBM were evaluated and compared. These models were trained using a dataset generated from full-wave electromagnetic (EM) simulations, and the Random Forest model exhibited the best predictive accuracy, with an R² value of 0.99. Additionally, a low-cost and scalable fabrication approach was demonstrated to realize conductive traces on PDMS, and a functional prototype was manufactured and tested. The prototype demonstrated consistent performance, with measured gain of 3.2 dB. An electrical equivalent lumped-element circuit model was also formulated to analytically validate the antenna’s EM simulation results. This integrated approach of data-driven optimization, low-cost fabrication, and circuit-level validation contributes to the practical realization of flexible RF antennas.
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    Tunable dual-functional metasurface for wideband cross-polarization conversion and wideband absorption
    (Elsevier B. V., 2023-10-24) DS, Chandu; Nagini, K.B.S. Sri; Soh, Ping Jack; Karthikeyan, S.S.
    This work presents a tunable and wideband dual-functional metasurface (DFM) operating in the terahertz regime with highest overlap bandwidth (OBW). The structure consists of a double-split ring resonator and a meandered square ring resonator based on VO2 to achieve reflective cross-polarization conversion and absorption functionalities, respectively. When the phase changing material VO2 is in its metallic state, the metasurface acts as a perfect absorber with a peak absorption of ≥ 90% over the operating band of 2.3–4.01 THz. When VO2 is in its insulating state, the metasurface acts as a reflective cross-polarization converter over a wideband from 1–4.1 THz with high polarization conversion ratio of ≥ 90%. The proposed DFM has a stable response up to 45∘ of incidence in the polarization converter state and 60∘ of angular stability under the absorber state. Further, tunability is achieved by integrating photoconductive silicon and controlling the optical pump intensity in the double-split ring and meandered. square ring resonators. The proposed metasurface finds its applications in security, detection and THz communication systems.